Conventionally, a so-called AC driving method is applied to many active matrix type liquid crystal display devices. This technique provides countermeasures against a deterioration phenomenon that when liquid crystal is driven by a DC for an extended period of time, material properties of the liquid crystal change and its resistivity decreases, by alternating the polarity of a drive voltage applied to the liquid crystal frame by frame, a more detailed and basic operation of which is disclosed on pages 69 to 74 of ‘Liquid Crystal Display Technology—Active Matrix LCD’ (Shoichi Matsumoto, Nov. 14, 1997, 2nd impression, Sangyotosho Publishing Co., Ltd.), etc.
According to this AC driving method, flickering would originally occur when the polarity alternating frequency of the drive voltage becomes half of the frame frequency, but by spatially and temporally averaging the polarity alternation within a screen, the fundamental wave component of optical response ripple is set to equivalent to or greater than the frame frequency, thus preventing flickering (visible flickering). More specifically, drive voltage polarities of pixels adjacent to (or pixel row or pixel column adjacent to) an arbitrary one pixel are differentiated from one another and their polarities are alternated frame by frame.
Since this AC driving method has a high polarity alternation rate of the drive voltage, there is a problem that the driving circuit requires great power consumption. The present inventor proposed to change an output sequence of image data from a source driver using a RAM to solve this problem in Unexamined Japanese Patent Publication No. 2003-114647.